Be worried if your GF starts shouting "Wasserbomb!"
I would move everything out from underneath it and leave it until the landlord has had a look, after all, it's to him you pay the rent, and he should (in an ideal world) be beholden to fix it.
(Says the man who is living in a half doubled glazed house with some horrendous cracks in the walls and an aga that tries to kill us if we use it. Thank you Mrs Landlord
)